This invention relates to an ultrasonic angioplasty device for insertion into arteries for treating of obstructions caused by plaque and thrombi and more particularly to a vascular catheter which combines balloon dilatation capabilities with ablation through ultrasonic treatment of such obstructions.
One of the obstructions encountered in percutaneous transluminal angioplasty is thrombus or a blood clot which develops within the artery and the other is plaque which is present in the wall of the artery. Occasionally during balloon angioplasty the migration of large particles of thrombus material or plaque results either in damage to the blood vessel wall or movement of loose material into the blood vessel lumen causing reclosure or closure of other vessels. Similarly, it is sometimes difficult to dispel a large thrombus burden.
There have been a number of patents dealing either with the balloon angioplasty in combination with ultrasonic imaging means or with balloon angioplasty combined with removal of plaque and/or thrombi.
U.S. Pat. No. 4,924,863 to Sterzer describes a method of removing plaque using two juxtaposed catheters in a vas. At the distal end of one catheter is a balloon which is inflated asymnetrically so that it presses against one side of the vas. The other catheter includes a heating element which, when the balloon is inflated presses the heating element against the region of plaque to be treated. Just enough heat is applied through microwave or radio frequency energy to cause some melting of the fatty plaque deposit. Suction is then applied to the second catheter to pull the liquefied plaque material out from the proximal end of the catheter. Where the plaque has become calcified, an ultrasonic transducer is substituted for the heating element and is employed to ablate material from the surface of the plaque deposit and the ablated material is removed by suction applied to the proximal end of the second catheter.
U.S. Pat. No. 5,195,955 to Don Michael shows a catheter in an artery obstructed by plaque and/or thrombus. The catheter includes a balloon designed to inflate asymmetrically, but to seal off the artery except for limited flow through one lumen of the catheter. Ports are supplied on opposite sides of the inflated balloon which permit limited flow of blood through the lumen, but the balloon seals off the artery so that debris from a separate procedure operating proximally of the balloon to remove the obstruction does not flow downstream. A separate lumen is described for applying suction to remove the debris.
U.S. Pat. No. 5,118,831 to Yue-Teh Feng et al shows a vascular catheter with tandem imaging and dilatation components located in its distal end. Separate lumens within the catheter permit different fluids to be used for inflating the balloon and for ultrasonic imaging. A rotatable cable drives a rotatable scanning mirror which receives sonic signals from an adjacent transducer. This patent describes a straightforward angioplasty procedure enhanced by the use of an ultrasonic scanning device in the same catheter.
A recent article in The Journal of Invasive Cardiology, Vol. 10/Supplement A dated Mar. 10, 1998 entitled xe2x80x9cMechanical Thrombectomy in Acute Ischemic Syndromes: Cufters, Suckers, and Bustersxe2x80x9d by Jeffrey W. Moses M. D. deals with many of the above problems and with methods and apparatus for dealing with such problems.
It seems clear that although many techniques have been devised for dealing with the problems discussed above, none are universally useful. While one method or technique may be helpful in one situation, it may not help in another. In particular there is a need for a device or apparatus which can remove or substantially ameliorate plaque and thrombi deposits while minimizing the danger from migration of large particles of debris.
A unique feature of the present invention is the mounting of an ultrasonic device on the distal end of the catheter inside the span of the balloon on the catheter so that the balloon, when inflated, can focus and deliver ultrasound energy to two pathologic sites within the artery, i.e., the thrombus and the plaque sites. By focusing or concentrating ultrasound energy to the thrombus and the plaque deposits, the thrombus can be caused to disintegrate into microscopic sized particles which can pass into the circulatory system without damage to other vessels downstream. At the same time, or during the same procedure, the concentrated ultrasonic energy tends to fracture and thereby soften plaque deposits.
Depending upon the nature of the obstruction, the cardiologist may be concerned that larger sized thrombus particles or plaque particles may escape downstream and cause blockage of additional vessels. Applicant has devised a catheter arrangement utilizing a second balloon on the catheter distal of the first balloon thereby defining a chamber within the artery and between the balloons into which any such larger particles are contained. A port in the catheter wall communicates with this chamber and is connected to a source of negative pressure for drawing the debris from the chamber and out the proximal end of the catheter.
Another embodiment of this invention utilizes an expandable umbrella-like element carried on the catheter downstream of the balloon and the ultrasonic transducer. This device, which may constitute a filter capable of passing normal blood, is expanded at the time the ultrasonic transducer is energized to trap any larger particles, preventing them from moving downstream. At the end of the procedure, the umbrella-like element is collapsed around the larger particles which are then removed along with the catheter.